1. Field of the Invention
This invention relates to the addition of fluorinated amphoteric surfactants to aqueous basic solutions to yield developers for alkali developable photoresists. The addition of the surfactant lowers the surface tension of the developer for improved wetting without detrimental effects on resist photospeed, profile, depth of focus and resolution.
2. Background Art
A common method of developing photoresists consists of applying a small volume of developer to a resist film which is oriented parallel to the ground. The developer may be applied in a stream or by spraying. The developer forms a pool (puddle) on top of the resist and is allowed to remain until the end of the development cycle. The developer is then removed typically by a combination of spinning and aqueous rinsing.
U.S. Pat. No. 3,891,439, issued Jun. 24, 1975, is directed to a developer composition for lithographic printing plates which comprises an aqueous solution comprised of from about 5% by weight to 30% by weight of an amphoteric 2-alkyl substituted imidazoline surfactant and from 5% by weight to 25% by weight of a water-soluble organic lithium salt.
U.S. Pat. No. 4,464,461, issued Aug. 7, 1984, is directed to a developing composition for use in developing an image-wise exposed layer of a light sensitive quinone diazide composition, the composition comprises a quaternary alkynol ammonium hydroxide developing agent in a stabilizing concentration of a semicarbazide.
U.S. Pat. No. 4,610,953, issued Sept. 9, 1986, is directed to an aqueous developer solution for a positive-type photoresist which comprises 0.5% to 3% by weight, based on the developer solution of tetramethylammonium hydroxide, 1% to 4% by weight based on the developer solution of trimethylhydroxyethyl ammonium hydroxide and water as a solvent for the two components.
U.S. Pat. No. 4,613,561, issued Sept. 23, 1986, is directed to a developer for a positive photoresist which comprises a formulation of an aqueous alkali-base such as potassium hydroxide, in a fluorocarbon or carboxylated surfactant.
U.S. Pat. No. 4,628,023, issued Dec. 9, 1986, describes an aqueous metal ion-free developer composition for developing photoresist which comprises a metal ion-free alkali in a metal ion-free surfactant that is a quaternary ammonium compound.
U.S. Pat. No. 4,661,436, issued Apr. 28, 1987, describes a positive photoresist metal ion aqueous developer which comprises a formulation of an aqueous alkali base such as potassium hydroxide and a fluorocarbon surfactant.
U.S. Pat. No. 4,710,449, issued Dec. 1, 1987, describes a developer which contains an organic base and a particular fluorocarbon surfactant.
U.S. Pat. No. 4,741,989, issued May 3, 1988, describes a developer for positive photoresist which comprises an aqueous solution of a particular quaternary ammonium hydroxide in at least one development modifier selected from the group consisting of water-soluble aliphatic ketones, cyclic ethers, and tertiary amines.
U.S. Pat. No. 4,784,937, issued Nov. 15, 1988, describes a developing solution for positive-working photoresist composition which comprises an aqueous medium, an organic basic compound free from metal ions in an amount sufficient to obtain a pH between 11.0 and 13.5 and a fluorine-containing surface active agent.
U.S. Pat. No. 4,806,453, issued Feb. 21, 1989, describes an aqueous alkali developer for development of an exposed bottom resist layer of a bilayer photoresist film. The developer is an aqueous alkaline solution of a tetra alkyl ammonium hydroxide having at least two alkyl groups with two or more carbon atoms and is preferably tetra ethyl ammonium hydroxide.
U.S. Pat. No. 4,820,621, issued Apr. 11, 1989, describes an aqueous developer solution for a positive-working photoresist composition comprising a water-soluble organic base compound in a specific nonionic surface-active agent which may be an alkyl substituted phenyl or naphthyl ether of polyoxyethylene glycol in a specified concentration.
U.S. Pat. No. 4,914,006, issued April 3, 1990, describes a positive resist developer comprising a solution containing a quaternary ammonium hydroxide, a cationic surfactant, and a nonionic surfactant.
Japanese Publication No. 55-66909 describes a developing solution for positive type photoresists. The develoPing solution consists of tetramethyl ammonium hydroxide to which is added a novolak-type phenol resin.
Substrate size in the semiconductor industry has increased over the years. A consequence of this increase in size is an increase in the difficulty in wetting all parts of the resist quickly and evenly in less than one second. Failure to maintain even wetting can lead to uneven development, poor reproducibility and subsequent poor device performance. Surfactants can lower the surface tension and improve wetting of the photoresist by the developer leading to even development. However, most surfactants degrade photoresist profiles and/or resolution and/or depth of focus and/or photospeed.